The foldable mobile phone widely used recently is used in many cases for email or as a TV telephone, and further, is used to download a variety of information, such as music and video images, by using the Internet as well as being used as a voice phone to carry out voice communication. In particular, when a user downloads a large volume of images, it is important to increase the transmission rate of the downlink communication of the mobile phone (that is, the communication from the telephone station to the user terminal). In the communication system of the CDMA (Code Division Multiple Access) scheme now in service widely, the maximum transmission rate of downlink communication is 384 kbps and, with such a communication rate, a considerable time and communication cost are required if the user downloads a large volume of moving images etc.
Now, in the HSDPA (High Speed Downlink Packet Access), which is one of the high speed packet communication techniques being developed recently, even when a frequency bandwidth of 5 MHz is used, which is the same as the current CDMA scheme, it is possible to realize high speed communication of up to 14.4 Mbps that is more than five times the current communication speed. By this means, by using the HSDPA, even when downloading a large volume of images, it is possible to perform the process in a short time and at a low communication cost. The adaptive modulation scheme is important in order to increase the communication speed in this way. The adaptive modulation scheme is one, in which a fluctuating condition of a radio channel, that is, a change in the degree of radio wave propagation in the air is determined comprehensively and the most optimum modulation scheme is selected automatically. Specifically, a low-rate modulation scheme is used when the reception condition of radio waves is poor, and a high-rate modulation scheme is used when the reception condition is good. Therefore, in order to realize the HSDPA, improvement in reception performance in a multipath propagation environment of a mobile phone is important. For this reason, in order to improve such reception performance, improvement in reception performance is realized by allowing the base station to be mounted a plurality of antennas and reception system circuits and perform combining reception.
On the other hand, when carrying out voice communication using a mobile phone or when performing data communication such as an email or a TV telephone, a state in which a user holds the mobile phone in the hand and carries out voice communication by placing the mobile phone near the ear (hereinafter, referred to as a “voice communication state”) or a state in which a user holds the mobile phone in front of the user's chest to perform email operations (hereinafter, referred to as an “operation state”) is general. For such a variety of use states, an antenna switching diversity operation is utilized, in which a plurality of antennas provided at comparatively distant portions from the mobile phone main body are switched in accordance with the use state. With such an antenna switching diversity scheme, however, it is difficult to realize a high speed transmission in downlink communication.
Therefore, in order to cope with such a challenge in high speed transmission, techniques that have made various improvements to an antenna of a mobile phone have been proposed. For example, in patent document 1 below, a configuration is proposed, in which a plurality of antennas are incorporated inside a mobile phone and power is distributed to the antennas. In addition, in patent document 2 below, a configuration is proposed, in which two dipole antennas are provided in parallel inside a mobile phone and feeding phases of the dipole antennas are controlled. Further, in patent document 3 below, a configuration is proposed, in which a helical antenna outside a mobile phone and an antenna built in a flip are provided, and feeding phases of the antennas are controlled. These techniques of the patent publications also take measures to reduce influences of radio waves on a human body.    Patent Document 1: Japanese Patent Application Laid-open No. 2002-77006    Patent Document 2: Japanese Patent Application Laid-open No. 2002-152115    Patent Document 3: Japanese Patent Application Laid-open No. 2002-64314